Ports SystemModalContainerLayoutManager to ash/common

ash/common/wm/container_finder.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/wm/container_finder.h"
 
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/always_on_top_controller.h"
 #include "ash/common/wm/root_window_finder.h"
@@ skipping 90 matching lines @@
       return target_root->GetChildByShellWindowId(
           kShellWindowId_DragImageAndTooltipContainer);
     default:
       NOTREACHED() << "Window " << window->GetShellWindowId()
                    << " has unhandled type " << window->GetType();
       break;
   }
   return nullptr;
 }
 
+std::vector<WmWindow*> GetContainersFromAllRootWindows(
+    int container_id,
+    WmWindow* priority_root) {
+  std::vector<WmWindow*> containers;
+  for (WmWindow* root : WmShell::Get()->GetAllRootWindows()) {
+    WmWindow* container = root->GetChildByShellWindowId(container_id);
+    if (!container)
+      continue;
+
+    if (priority_root && priority_root->Contains(container))
+      containers.insert(containers.begin(), container);
+    else
+      containers.push_back(container);
+  }
+  return containers;
+}
+
 }  // namespace wm
 }  // namespace ash